Device for the contact-free support of a web of material

ABSTRACT

For supporting a web of material in a contact-free manner and also for drying the material, a U-shaped box-like member is arranged so that its open side faces toward the surface of the web to be supported. An air baffle plate is positioned in the open side of the box-like member and has a curvilinear shape along each of its edges located closely adjacent to the opposite closed sides of the box-like member. The spacing between the opposite sides and the curvilinear surfaces of the air baffle provide openings through which air is directed so that it follows the curvilinear surface of the air baffle and provides a cushion between the air baffle and the web. The air baffle can be formed in various ways, for example, by a pair of spaced tubular members joined by a plate member, by an oval shaped member and by a plate member with curved edges joined by a flat or undulating section.

United States Patent [191 Norfolk Apr. 30, 1974 DEVICE FOR THECONTACT-FREE SUPPORT OF A WEB OF MATERIAL [75] Inventor: Douglas J.Norfolk, Koniz BE,

[21] Appl. No.: 204,203

[30] Foreign Application Priority Data Dec. 4, 1970 Sweden 16475/70 June1, 1971 Sweden 7059/71 [52] US. Cl. 34/156, 226/97 [51] Int. Cl. F26!)13/20 [58] Field of Search 34/156, 10; 308/DIG. l; 226/97, 7; 239/DIG.7, 590.5; 302/29 [56] References Cited UNITED STATES PATENTS 3,622,05811/1971 Vits 226/97 3,549,070 12/1970 Frost 34/156 3,452,447 l/l969Gardner 34/156 3,448,907 6/1969 Otepka et al.. 34/156 3,384,282 5/1968Vits 34/156 3,041,739 7/1962 Mgier-Windhorst... 34/156 3,367,581 2/1968Kizilos et a1. 239/D1G. 7

FOREIGN PATENTS OR APPLICATIONS 1,145,572 3/1963 Germany 34/156 OTHERPUBLICATIONS Scientific American, June 1966, pg. 84-92, Vol. 214, No. 6,Applications of the Coanda Effect.

Germany 34/156 Primary Examiner-Meyer Perlin Assistant ExaminerPaulDevinsky Attorney, Agent, or Firm-Toren and McGeady ABSTRACT Forsupporting a web of material in a contact-free manner and also fordrying the material, a U-shaped box-like member is arranged so that itsopen side faces toward the surface of the web to be supported. An airbaffle plate is positioned in the open side of the boxlike member andhas a curvilinear shape along each of its edges located closely adjacentto the opposite closed sides of the box-like member. The spacing betweenthe opposite sides and the curvilinear surfaces of the air baffleprovide openings through which air is directed so that it follows thecurvilinear surface of the air baffle'and provides a cushion between theair baffle and the web. The air baffle can be formed in various ways,for example, by a pair of spaced tubular members joined by a platemember, by an oval shaped member and by a plate member with curved edgesjoined by a flat or undulating section.

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zlw m/roz v 0006148 I Mae/0m DEVICE FOR THE CONTACT-FREE SUPPORT OF AWEB OF MATERIAL SUMMARY OF THE INVENTION The present invention isdirected to a device for contact-free support and drying of a web ofmaterial and, more particularly, it concerns the configuration of thedevice for directing air so that it provides the necessary supportwithout any direct mechanical contact or influence on the web ofmaterial.

Various apparatuses are known for supporting webs of material, mainlysuch apparatuses use nozzles which blow air directly against the web ofmaterial either perpendicularly or obliquely to it and frequently alsoinclude mechanical means for supporting the web.

Further, it has been known to arrange nozzle boxes on the opposite sidesof the material web. In the German Auslegeschrift l,l93,468 a suspensiondrier is described which employs staggered nozzle boxes and anundulating web guide to avoid curving or warping of the web in thetransverse direction.

Moreover, a suspension drier is disclosed in German Auslegeschrift1,729,222 in which the nozzle boxes are staggered in the direction ofthe web and also have a convex curvature in the same direction andbaffle plates are arranged on the transverse walls and form slottednozzles for the moving web. However, a vibration-free guidance of theweb is not assured with such suspension driers. Therefore, it is theprimary object of the present invention to eliminate the disadvantagesexperienced in the prior art and to provide a device for contact-freesupport of a web which is relatively free of vibrations.

In accordance with the present invention, a web of material is supportedin a contact-free manner by means of box-like members which direct airbetween a baffle plate and the web for supplying an air cushion and alsofor using the air to dry the web. Preferably, the box-like member has aU-shaped configuration with its open side facing toward the web and withthe air baffle positioned within the open side and spaced along itsedges from the adjacent sides of the box-like member. The edges of theair baffle adjacent the sides of the boxlike member have a curvilinearshape and are spaced from the adjacent side surfaces to provide narrowelongated slot-like openings through which air can be directed. Becauseof the curvilinear configuration of the baffle at the slot-likeopenings, air discharged from the boxlike member flows over the curvedsurfaces and is directed across the baffle toward the opposite opening.

Various arrangements of the air baffle can be provided such as a pair ofspaced tubular members interconnected by a plate member, an oval shapedmember and a plate member having either a flat or undulating surfacebetween the curvilinear surfaces defining one side of the slot-likeopenings from the box-like member.

Preferably, the box-like members from which the air is directed arearranged across the opposite surfaces of the web with the air bafflesarranged in staggered relationship. The invention is intended primarilyfor use in the paper, film and foil industries where piece material or aweb of material is coated on one or both sides or where several webs arecombined and subsequently transported through a passageway, tunnel orsimilar structure for drying, polymerization, fusion, baking, materialchanges, and the like.

The device in accordance with the present invention, can be adaptedindividually or in groups to meet the requirements of the individualoperation being effected on the web, for instance, drying, cooling,heating and supporting.

Unlike many known devices, the present invention affords a device whichprovides vibration-free guidance in the longitudinal or transversedirection of a stationary material web or of a web moving at any desiredspeed.

By arranging the device both above and below the web, the web tensioncan be varied within a wide range, that is by the range of tensionproduced by the air flowing from the nozzle-like openings in the device,and such variation can be altered without impairing the supporting orcarrying properties of the device.

Since the device can be used for webs of thin foils or of thickcardboard and in instances where the overall height of the device mustbe'limited, numerous tests have indicated that the device yields optimumresults in accordance with the intended use.

The various features of novelty which characterize the invention arepointed out with particularly in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is a sectionalview of one embodiment of the present invention taken along the line A-Bin FIG. 3;

FIG. 2 is a schematic view of a plurality of devices such as shown inFIG. 1 arranged in staggered relationship on the opposite sides of a webof material;

FIG. 3 is a top view of the embodiment of the present invention shown inFIG. 1; 7

FIG. 4 is a longitudinal sectional view taken along the line C-D in FIG.3;

FIG. 5 is a longitudinal sectional view taken along the line E-F in FIG.3;

FIG. 6 is a side view of another embodiment of the present invention; 1

FIG. 7 is a schematic side view of a device embodying the arrangementshown in FIG. 6 with the device for supporting the web being locatedabove and below its surface;

FIG. 8 is a view, similar to FIG. 6, of still another embodiment of thepresent invention;

FIG. 9 is a side view, similar to that in FIG. 7, of devices embodyingthe arrangements of FIG. 8 arranged opposite both surfaces of a web ofmaterial;

FIG.S 10,11 and 12 are views similar to FIGS. 6 and 8 showing stillfurther embodiments of the present invention;

FIG. 13 is a side view of devices embodying the arrangement as shown inFIG. 12 for supporting the opposite surfaces of a web; FIG. 14 is a viewof yet another embodiment of the present invention; and

FIG; 15 is a side view of a pair of oppositely disposed devicesembodying the arrangement shown in FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION In FIGS. 1 to a device is shownfor supporting a web of material. The device includes a U-shapedbox-like member 4 open on its face or side directed toward the web 14.Supported within the U-shaped member 4 are a pair of laterally spacedtubular members 1,2 arranged so that their outer surfaces are spacedclosely from the adjacent inner surfaces of the legs 9 of the U-shapedmember. Due to the relative arrangement of the tubular members 1 and 2and the adjacent inner surfaces of the box-like member 4, a pair ofchambers 3 extend along each of the legs 9 of the box-like member. Thetubular members 1,2 combine with a supporting plate 5 to provide an airbaffle facing toward the web 14. The supporting plate 5 has a flattenedV-shaped configuration in a plane extending in parallel relationshipwith the legs of the box-like member, note FIG. 5. The point or apex ofthe V-shaped plate is located intermediate the ends of the plate,approximately midway between the ends of the tubular members 1,2, and islocated more remotely from the web 14 than the surfaces of the platewhich extend from the point to the opposite ends of the box-like member.The surfaces of the plate 5 converge toward the web as they extendoutwardly toward the ends of the tubular members. Each of the surfacesof the plate 5 extending from its point has a longitudinally extendingslot 6 extending generally in parallel relationship with the axes of thetubular members. The sides of the slots diverge from one another as theslot extends toward the ends of the tubular members. At the ends of thebox-like member 4, cover plates 7 form closures for the ends of thetubular members and for the chambers 3. Accordingly, narrow elongatedslot-like openings 10 are provided between the inner surface of the freeends of the legs 9 and the juxtaposed surface of the tubular members1,2.

As shown in FIGS. 1 and 4, inlet lines 11 and 12 extend through the wallof the box-like member into the tubular members 1 and 2 for supplyingair therein. Each of the tubular members has a slot-like opening 13 forcommunicating the interior of the tubular member with one chamber 3.Accordingly, air flows through the inlet lines 11 and 12 into thetubular member 1,2 and then flows from each tubular member through theslotlike openings 13 into the chambers 3 and then through the nozzle orslot-like openings 10 toward the web and along the outer periphery ofthe tubular members. As can be seen in FIG. 1, the air flows over thecurvilinear surface on the exterior of the tubular members after itspassage through the nozzles 10 and flows inwardly toward the othertubular member and is removed through the slots 6.

METHOD OF OPERATION (FIGS. 1 THROUGH 5) The flow of air from the nozzlesor slot-like openings 10 passes, for aerodynamic reasons, over thecurvilinear surfaces on the exterior of the tubular members and combinesto provide an air cushion between the web and the baffle provided by thetubular members 1,2 and the plate 5. The pattern of the flow of air isshown in FIGS. 1 to 5 and the greatest pressure is provided in thecenter of the device. Due to the lateral flow the web of material issmoothed out in the transverse direction. Additionally, the rapidlyflowing air contacts the web over a considerable distance and leads toeffective utilization, particularly for drying action. The portion ofthe air which does not flow along the curvature of the tubular memberscontributes a drying effect as it contacts the web. Accordingly, the airis excellently utilized from its issuance from the slot-like openings 10until it is sucked off or returned for circulation on the side of theweb.

If webs of different widths are used, the lateral outflow of airpresents problems with increasing web width. To avoid this problem, theoutwardly widening slots 6 are provided in the support plate 5. The airpassing through these slots is drawn into the circulation system fromthe chamber between the plate 5 and the wall of the box-like member 4 bymeans of an exhaust system (not shown).

Based on the arrangement illustrated in FIGS. 1 to 5 and using theeffect of the air on the web without any direct mechanical influence orcontact, it has been found that different arrangements are possible,depending on the intended use for the device. The embodiment shown inFIGS. 1 to 5 is characterized in that the air bafile is arranged betweenat least two oppositely disposed walls of a box-like member and thecurvilinear surfaces of the baffle and the side walls of the box-likemember provide a pair of nozzles or slot-like openings for directing theair outwardly so that it follows the curvilinear surface of the airbaffle located at the opening. Due to the arrangement of the curvilinearsurfaces of the baffle, the air from each of the nozzles or openingsflows toward the other and provides the desired air cushioning effect.

The shape or configuration of the air baffles is selected in accordancewith the type of material forming the web and several typicalembodiments are shown in the drawings in FIGS. 6 to 15.

In FIG. 6 another embodiment of the device is illustrated in which theoval shaped baffle plate 4A is positioned within the open side of aU-shaped box-like member 3A with the baffle plate extending between thefree ends of the side walls lA,2A so that the curvilinear surfaces 7A,8Aof the plate project outwardly from the ends of the side walls towardthe web 9A. The curvilinear ends of the baffle plate 4A and the freeends of the adjacent side walls 1A,2A form elongated nozzles orslot-1ike openings 5A, 6A for directing air supplied into the boxJikemember 3A. Due to the curvilinear configuration of the end surfaces7A,8A of the baffle plate, the air flows from the openings 5A,6A aredirected toward each other. Hot or cold air supplied into the box-likemember 3A flows in the direction of the arrows at a high speed passingthrough the openings 5A, 6A and is directed toward the web of material9A with a portion of the air following along the surface of the baffleplate 4A and providing the boundary layer effect or cushioning for theweb.

As indicated above, the baffle plates 4A shown in both FIGS. 6 and 7,are represented as oval shaped members or bodies so that a curvilinearsurface is provided at each of the nozzles or openings from the boxlikemember. In FIG. 7 an arrangement is shown with a box-like member 10Alocated on the opposite sides of the surface of the web 9 and theopenings in the boxlike members containing the nozzle plates arestaggered or offset on the opposite sides of the web. As the web 9Apasses between the two box-like members A, it is supported and spacedfrom the baffle plates by the flow of air conducted through the box-likemembers and outwardly through the openings extending along thecurvilinear surfaces of the baffle plates.

In FIGS. 8 and 9 another embodiment of the baffle plate is shown whichconsists of a pair of laterally spaced cylindrical bodies 11A joinedtogether by a plate 12A fixed to and extending along the surfaces of thecylindrical bodies which are located more closely to the web 9A. As inFIG. 7, the openings from the boxlike members 10A on the opposite sidesof the web 9A in FIG. 9 are offset relative to one another to effect thedesired support arrangement. In FIGS. 8 and 9, the free ends of the sidewalls 1A,2A are directed inwardly toward the curvilinear surfaces 7A, 8Aof the cylindrical bodies 11A forming a constricted opening anddirecting the air flowing from the nozzles 5A, 6A over the curvilinearsurfaces 7A,8A.

In FIG. 10 a baffle plate is provided with an undulating or wave-shapedconfiguration having the curvilinear surfaces 7A and 8A located adjacentthe nozzle or slot-like openings 5A,6A from the box-like member and withan additional wave-shaped section extending between the two curvilinearsurfaces 7A,8A. As with the other embodiments discussed above, thecurvilinear surfaces 7A,8A direct the air from the openings 5A,6A sothat it flows toward the web and in a cushionlike effect between thebaffle plate and the web.

In FIG. 11 the baffle plate has the curvilinear surfaces 7A, 8A locatedadjacent the slot-like openings 5A,6A from the box-like member, however,instead of the undulating form of section joining the curvilinearsurfaces, a flat planar section is provided which is recessed inwardlytoward the box member, that is away from the curvilinear surfaces 7A, 8Aand the surface of the web.

In FIG. 12 another embodiment of the baffle plate is shown similar tothat set forth in FIG. 11, but the flat planar section which connectsthe curvilinear surfaces 7A, 8A extends in a plane containing the endsof the curvilinear surfaces located closer to the web. In theembodiments of FIGS. 10, 11 and 12, the air flows outwardly from thebox-like member through the restricted nozzle or slot-like openings 5A,6A and then passes at least in part over the curvilinear surfaces 7A, 8Aalong the opposite edges of the baffle plate for providing the aircushion between the baffle plate and the web 9A.

In FIG. 13 a pair of box-like members are positioned on the oppositesides of the web 9A and are provided with baffle plates formed in thesame manner as the baffle plates in FIG. 12. As in the arrangementsshown in FIGS. 7 and 9, the openings from the box-like members 10A inwhich the baffle plates are located are offset relative to one anotheron the opposite sides of the web.

Still another embodiment of the invention is shown in FIGS. 14 and 15 inwhich inverted L-shaped sections 15A are located on the interiorsurfaces of the sides 1A,2A adjacent their free ends. In combinationwith the ends of the sides 1A, 2A, the L-shaped sections 15A formelongated grooves or pockets into which the edges of the baffle plateextend and from which the curvilinear surfaces 7A,8A project toward thesurface of the web. As with the embodiment of the baffle plate shown inFIGS. 12 and 13, a flat planar section extends between the ends of thecurvilinear sections 7A, 8A. As indicated in FIGS. 14 and 15, the airentering the boxlike members flows outwardly through the grooves 13A,14A formed between the ends of the sides IA, 2A and the L-shapedsections 15A, reversing direction about the ends of the curvilinearsections 7A, 8A and being directed outwardly over the curvilinearsurfaces for passage between the flat surface of the baffle plate andthe opposed surface of the web. In FIG. 15 the boxlike members 10A areprovided on the opposite sides of the webs with multiple openingscontaining baffle plates of the type shown in FIG. 14. As with the otherbox-like members 10A containing multiple openings for the baffle plates,the openings are offset relative to one another on the opposite sides ofthe web.

The main characteristic of the present invention incorporated into eachof its embodiments is the curvilinear surfaces provided along the edgesof the baffle plate adjacent the sides of the box-like member throughwhich the air flows prior to passing between the baffle plate and theweb. The baffle plate is spaced from the sides of the box-like member sothat nozzles or slot-like openings (in FIG. 1 reference numeral 10, inFIGS. 6 to 15 reference numerals 5A,6A) are provided so that the jets ofair issuing through the openings follow the curvilinear surfaces of theair baffle and flow toward each other. After the air has been introducedbetween the baffle and the web, it must continue to flow because of thecontinuous supply of air from thebox-like members. Accordingly, thereare two possibilities for the discharge of the air from between thebaffle plate and the web, in one instance the air must reverse itself by180 degrees and flow out in the opposite direction from which it came.Alternatively, the air being supplied forces the air ahead of it in theaxial direction of the device from the center toward the sides.

In fact, the outflow of air from between the baffle and the web combineboth of the above types of flow, however, they are slightly mixed at theends of the device.

Since it is difficult for the air to either reverse itself by l or topush the cushion of air ahead of it, both of these air flows encountersome resistance. In accordance with the invention, a chamber is formedfor the length of the nozzles or slot-like openings having the dimensionof the distance between the baffle plate and the web and also the widthof the web and in the chamber the pressure is higher than atmosphericpressure so that it places the web of material under tension and carriesit in a contact-free manner. In accordance vgith the tension acting onthe web and the lift which results from the amount of air suppliedbetween the web and the baffle plate, thedistance from the web to thebaffle plate adjusts itself automatically to a dynamic equilibrium whichhas highly balanced flow conditions and, as a result, ensures apractically vibration-free support of the web.

If the process in which the web is involved is stopped for productionreasons, the amount of air can be reduced to about 5 percent of theusual amount used, because it has been found that this amount issufficient for supporting the web so that it does not touch thestructure from which the air flows. This arrangement leads to aneconomical consumption of air and prevents overdrying of the web duringshort work stoppages.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the ap- 7 plication of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. A device for supporting a web of material in a contact-free manner sothat it is maintained in a spaced position from the device, comprising abox-like member open at least on the side directed toward the web to besupported and closed along two opposite sides which extend along theopen side and with the closed sides extending angularly from the openside away from the web, an air baffle positioned within and extendingacross the open side of said box member and closely spaced along two ofits opposite edges from said two opposite sides of said box-like memberand forming therebetween narrow elongated slot-like openings, each ofsaid two opposite edges of said air baffle extending along saidslot-like openings having a curvilinear form from a first location atwhich it forms one side of said slot-like opening to a second locationspaced angularly from said first location and located in a planedisposed angularly to the plane of the adjacent said opposite side andextending in the general direction of the web to be supported, inletmeans for supplying air internally of said box-like member with the airflowing outwardly through said slot-like openings and over thecurvilinear surface of said baffle so that at least a part of the flowof air from each said slot-like opening is directed toward the otheralong the surface of said baffle facing toward the web, said air bafflecomprising a pair of tubular members having their axes disposed insubstantially parallel relationship with one another and with saidopposite sides of said box-like member, said inlet means comprises aninlet sleeve extending into each of said tubular members at a pointspaced from the open side of said box-like member and each of saidtubular members having a narrow elongated opening arranged to openwithin said box-like member for supplying air to said slot-like openingsfrom said box-like member.

2. A device for supporting a web of material in a contact-free manner sothat it is maintained in a spaced position from the device, comprising abox-like member open-at least on the side directed toward the web to besupported and closed along two opposite sides which extend along theopen side and with the closed sides extending angularly from the openside away from the web, an air baffle positioned within and extendingacross the open side of said box member and closely spaced along two ofits opposite edges from said two opposite sides of said box-like memberand forming therebetween narrow elongated slot-like openings, each ofsaid two opposite edges of said air baffle extending along saidslot-like openings having a curvilinear form from a first location atwhich it forms one side of said slot-like opening to a second locationspaced angularly from said first location and located in a planedisposed angularly to the plane of the adjacent said opposite side andextending in the general direction of the web to be supported, inletmeans for supplying air internally of said box-like member with the airflowing outwardly through said slot-like openings and over thecurvilinear surface of said baffle so that at least a part of the flowof air from each said slot-like opening is directed toward the otheralong the surface of said baffle facing toward said web, said box-likemember is U- shaped with the legs of said U-shaped member forming saidtwo opposite sides thereof, and said air baffle comprises a pair ofhollow cylindrically-shaped members having their axes disposed insubstantially parallel relationship with one another and with saidopposite sides of said U-shaped box-like member, and wherein saidcylindrically shaped members define said curvilinear form, saidcylindrically-shaped members being spaced apart and forming an openspace therebetween, and a plate member extending between and forming aclosure for the open space between said cylindrically-shaped members.

3. A device as set forth in claim 2, wherein said cylindrically-shapedmembers are tubular members, said plate member has a shape of aflattened V in a plane extending parallel to the axis of said tubularmembers with the point of its V shape located intermediate the ends ofsaid tubular members and its surfaces extending from the point slopingtoward the location of the web.

4. A device, as set forth in claim 2, wherein said plate member is aflat plate section fixed to and extending between saidcylindrically-shaped members and being located in a plane which includesthe surfaces of said cylindrically-shaped members spaced most closelyfrom the web.

5. A device, as set forth in claim 3, wherein each of said surfaces ofsaid plate member extending from its point having a slot thereinextending in parallel relationship with the axes of said tubular memberswhereby the flow of air from said slot-like openings between saidbox-like member and the web enter said slot in said plate member.

6. A device, as set forth in claim 5, wherein said slots and said platemember having the longitudinally extending sides thereof disposed indiverging relationship as they extend away from the point of saidV-shaped plate member.

1. A device for supporting a web of material in a contact-free manner so that it is maintained in a spaced position from the device, comprising a box-like member open at least on the side directed toward the web to be supported and closed along two opposite sides which extend along the open side and with the closed sides extending angularly from the open side away from the web, an air baffle positioned within and extending across the open side of said box member and closely spaced along two of its opposite edges from said two opposite sides of said box-like member and forming therebetween narrow elongated slot-like openings, each of said two opposite edges of said air baffle extending along said slot-like openings having a curvilinear form from a first location at which it forms one side of said slotlike opening to a second location spaced angularly from said first location and located in a plane disposed angularly to the plane of the adjacent said opposite side and extending in the general direction of the web to be supported, inlet means for supplying air internally of said box-like member with the air flowing outwardly through said slot-like openings and over the curvilinear surface of said baffle so that at least a part of the flow of air from each said slot-like opening is directed toward the other along the surface of said baffle facing toward the web, said air baffle comprising a pair of tubular members having their axes disposed in substantially parallel relationship with one another and with said opposite sides of said box-like member, said inlet means comprises an inlet sleeve extending into each of said tubular members at a point spaced from the open side of said box-like member and each of said tubular members having a narrow elongated opening arranged to open within said box-like member for supplying air to said slot-like openings from Said box-like member.
 2. A device for supporting a web of material in a contact-free manner so that it is maintained in a spaced position from the device, comprising a box-like member open at least on the side directed toward the web to be supported and closed along two opposite sides which extend along the open side and with the closed sides extending angularly from the open side away from the web, an air baffle positioned within and extending across the open side of said box member and closely spaced along two of its opposite edges from said two opposite sides of said box-like member and forming therebetween narrow elongated slot-like openings, each of said two opposite edges of said air baffle extending along said slot-like openings having a curvilinear form from a first location at which it forms one side of said slot-like opening to a second location spaced angularly from said first location and located in a plane disposed angularly to the plane of the adjacent said opposite side and extending in the general direction of the web to be supported, inlet means for supplying air internally of said box-like member with the air flowing outwardly through said slot-like openings and over the curvilinear surface of said baffle so that at least a part of the flow of air from each said slot-like opening is directed toward the other along the surface of said baffle facing toward said web, said box-like member is U-shaped with the legs of said U-shaped member forming said two opposite sides thereof, and said air baffle comprises a pair of hollow cylindrically-shaped members having their axes disposed in substantially parallel relationship with one another and with said opposite sides of said U-shaped box-like member, and wherein said cylindrically shaped members define said curvilinear form, said cylindrically-shaped members being spaced apart and forming an open space therebetween, and a plate member extending between and forming a closure for the open space between said cylindrically-shaped members.
 3. A device as set forth in claim 2, wherein said cylindrically-shaped members are tubular members, said plate member has a shape of a flattened V in a plane extending parallel to the axis of said tubular members with the point of its V shape located intermediate the ends of said tubular members and its surfaces extending from the point sloping toward the location of the web.
 4. A device, as set forth in claim 2, wherein said plate member is a flat plate section fixed to and extending between said cylindrically-shaped members and being located in a plane which includes the surfaces of said cylindrically-shaped members spaced most closely from the web.
 5. A device, as set forth in claim 3, wherein each of said surfaces of said plate member extending from its point having a slot therein extending in parallel relationship with the axes of said tubular members whereby the flow of air from said slot-like openings between said box-like member and the web enter said slot in said plate member.
 6. A device, as set forth in claim 5, wherein said slots and said plate member having the longitudinally extending sides thereof disposed in diverging relationship as they extend away from the point of said V-shaped plate member. 